You need an optionset for each slideshow. One optionset can be used for multiple slideshows when all the slideshows share the same transitions and other characteristics.

Add a new optionset

Title

Type in the A human-readable title for this option set. You can optionally edit the machine readable name.

Image style

I used the defaults. Options include None (original image), flexslider_full, flexslider_thumbnail, thumbnail, medium, and large. There is another option list for thumbnails.

Generate Slideshow and Animation Settings

Navigation and Control Settings

Advanced Options

Rename optionset

I tried to rename an optionset by editing the title and machine name but nothing changed. I then cloned the existing optionset to the new name and deleted the original.

If you change the machine name for an optionset, remember to check all the slideshows and change the optionset selected for the slideshow.